High temperature process vessels (e.g., furnaces, kilns, smelters and the like) are employed in a variety of industries. Typically, the wall surfaces of such high temperature process vessels have an internal coating or lining formed of a solid high temperature refractory material. Such internal refractory coatings or linings may sometimes need to be repaired, especially during the latter part of their operational duty cycles.
One well known technique to repair refractory wall surfaces of high temperature process vessels while at or near their high operational temperatures is colloquially referred to as “ceramic welding”. More specifically, ceramic welding techniques is carried out while the refractory lining is still hot so as to minimize downtime of the process vessel and to preclude cracking of the lining which might occur on cooling below its operational temperatures. In ceramic welding, a stream of welding particles (usually a particulate mixture of metals and metal oxides) is propelled in a stream of a gaseous fluid, preferably oxygen, through a fluid (typically water) cooled elongate lance. The particles impinge on the area of the refractory lining to be welded and, due to the elevated temperature of such lining, the particles fuse to form a ceramic weld thereat. In use, the lance is inserted into the process vessel while at or near its high operational temperatures, for example, at or near several hundreds of degrees Fahrenheit (e.g., about 500° F.) to up to several thousands of degrees Fahrenheit (e.g., from 1000 to up to about 3000° F.). The operator physically holds the proximal end of the lance outside the process vessel, and manipulates the lance as to position the distal end adjacent the area in need of welding. The operator is therefore shielded from the extreme high temperatures existing within the process vessel, but is nonetheless capable of directing the stream of particulates toward the refractory lining inside the vessel by virtue of the liquid-cooled lance. (See generally, U.S. Pat. No. 3,684,560, the entire content of which is expressly incorporated hereinto by reference.)
Some refractory linings are fibrous structures which have, prior to the present invention, not been repaired using ceramic welding or other hot repair techniques. In this regard, unlike the particulate materials which can be entrained in pressurized gas and propelled through the thermally protected lance, the precursor fibrous refractory material is typically in the form of a relatively viscous pumpable paste material. As such, the material can only be atomized just prior to being applied onto a surface. For such reason, fibrous refractory materials have previously been applied to process vessel surfaces while cold.
It would therefore be highly desirable if pumpable viscous (e.g., paste-like) fibrous refractory materials could be applied onto the internal surfaces while hot (i.e., while the process vessel is at or near its high operational temperatures). It is towards providing such techniques and systems that the present invention is directed.
Broadly, the present invention is embodied in systems and methods whereby pumpable viscous fibrous material may be applied onto surfaces of high temperature process vessels while hot (i.e., while at or near such vessels' high operational temperatures of several hundreds up to several thousands of degrees Fahrenheit).
More specifically, according to a preferred system for repairing fibrous refractory on walls of a high temperature process vessel according to the present invention, there are provided a lance having a nozzle structure at a distal end thereof, and a pump system for pumping a pumpable fibrous refractory material to the nozzle. The lance has length sufficient to allow the lance to be inserted into the high temperature process vessel so that the nozzle structure is adjacent an area in need of repair while an operator holds a proximal end thereof outside the vessel.
Most preferably, the lance of the present invention will a material supply tube in communication with the nozzle structure for directing the pumpable fibrous material from the pump system to the nozzle structure. Inlet and discharge cooling liquid conduits are provided in the lance to allow circulation of a coolant (e.g., water) through the lance to protect the lance from high temperatures within the process vessel. Importantly, an atomizing tube is provided as a component part of the lance so as to be in thermal communication therewith. The atomizing tube has an inlet at the proximal end of the lance so as to be positioned outside the process vessel, and a discharge end which fluid communicates with the material supply tube adjacent the nozzle structure. Introduction of an atomizing gas through the tube will therefore atomize the fibrous pumpable material upon discharge through the nozzle structure.
In use, according to the method of repairing a fibrous refractory wall of a high temperature process vessel according to the present invention, a protective liquid-cooled lance having an atomizing tube in thermal communication therewith is inserted into the process vessel while the process vessel is at or near its high operational temperature so that a nozzle structure of the lance at a distal end thereof is positioned adjacent to an area of the process vessel wall in need of repair, and so that the lance may be manipulated from outside the process vessel during repair of the wall thereof. A viscous fibrous refractory material may then be pumped from a source thereof from the proximal end of the lance to the nozzle structure at the distal end of the lance, while an atomizing gas is directed through the atomizing tube. In such a manner, the atomizing gas causes the flowable fibrous refractory material to be discharged from the nozzle structure of the lance in the form of an atomized spray. Manipulating the lance from outside the process vessel will thereby cause the atomized spray of the flowable fibrous material to contact the wall of the process vessel thereby repairing the same.
These, as well as other, aspects and advantages of the present invention will become more clear from the following detailed description of the preferred exemplary embodiments thereof.